Electronic devices comprising electronic analog, digital and/or mixed-mode circuits of an integrated circuit may require a certain minimum threshold voltage for proper operation. When a power source for these devices is below a critical operating voltage (e.g., “brown-out”), the circuits of a device may be in unpredictable “meta-stable” states and electrically noisy environments may further degrade operation of the device circuits when trying to operate below the critical operating voltage. A brown-out is considered to have occurred when the incoming voltage available to a device, e.g., microprocessor, has dropped to a level where the device should not continue operating, since errors or partly functional conditions may occur in its logic or storage elements. The brownout ends when the voltage has risen back above the brownout level. Electronic circuits have been used to monitor the voltage of a power source to an electronic device in order to detect a required voltage threshold in generating a brown-out-reset (“BOR”) for the digital logic of the electronic device. A brownout detector detects when the operating voltage has dropped to just above the brownout voltage level and produces a signal to indicate to the electronic device that a brownout is pending. The brownout signal may initiate a reset or freeze the operation of the electronic device in order to avoid improper operation thereof.
Typically BOR circuits require a quiescent current at all times in order to function. For low power or battery operated electronic devices, this quiescent current is a significant factor in the reduction of battery life, particularly for electronic devices that are expected to be operable for extended periods of time, e.g., devices operating at very low power levels when in a sleep mode. Thus, it is preferred that the quiescent current for a BOR circuit be held to a minimum for longest battery operation. On the other hand, however, it is also very important to prevent high speed digital logic from going into a BOR condition while mistakenly executing program instructions before the BOR signal is recognized and available for deactivation of the appropriate internal circuitry of the digital logic. This condition may potentially cause an electronic device failure because program instructions may be accessed and executed when the device is not operating within its proper voltage specifications.